Mainichi newspaper and Tokyo Metropolitan University measured daily food of 11 people living in 11 different locations.
The samples were taken from 11/13 ~ 11/15. They mixed 3 meals and snacks and then put them into a mixer and measured cesium by germanium semiconductor detector taking 2 hours.
The result shows in the worst case, you take 220 Bq of cesium from breakfast, lunch, dinner and snacks everyday non-stop.
Dateshi Fukushima 140 ~ 220 Bq per day
Takasakishi Gunma 30 ~ 81 Bq per day
Shiraishishi Miyagi 29 ~ 33 Bq per day
Below is a famous graph of ICRP. It shows how much radiation is stocked in your body if you keep having contaminated food everyday.
Abscissa axis = date
Vertical axis = Bq
The simplest put is, if you have 10 Bq from food everyday ,you become as contaminated as the 10 Bq food in 2 months. (If you weigh 50kg)